An X-ray CT device is a device for reconstructing a difference of X-ray absorptance within a patient, using data processing system, as an image. The X-ray CT device is provided with an X-ray source that irradiates a patient with X-rays, and an X-ray detector for imaging a patient that detects the X-rays transmitted through the patient, at a position opposed to the X-ray source, and images a difference of X-ray absorptance within the patient based on projection data in multiple directions acquired by carrying out image acquisition while rotating around the patient.
The X-ray detector of the X-ray CT device includes a plurality of detection elements. X-rays incident on the detection element are first converted by a scintillator in the detection element into photons (fluorescence). The converted photons are subject to photoelectric conversion by a photodiode in the same detection element and then processed as an electric signal in a circuit of subsequent stage. However, X-rays not incident on the detection element do not become an electric signal. For this reason, the X-ray detector of the X-ray CT device is configured to arrange as many as possible of the detection elements to reduce the part other than the detection elements, thereby enhancing sensitivity to X-rays and reducing ineffective radiation exposure.
Thus, the X-ray detector of the X-ray CT device is constituted by the plurality of detection elements, but as a result of communication of signals between the detection elements, an event called “crosstalk” by which the image blurs may occur. To cope with this, the X-ray detector is provided with separators interposed between the detection elements respectively, and reduces crosstalk by the separators. Crosstalk blocking capability of the separator depends on the thickness thereof, and making the separator thicker enhances the crosstalk blocking capability. On the other hand, since the separator cannot detect X-rays, the sensitivity of the X-ray detector is reduced with the separator being made thicker, to thereby increase ineffective radiation exposure.
Moreover, the X-ray detector of the X-ray CT device is provided with collimators on the side of the X-ray source in order to prevent X-rays scattered within the patient (scattered radiation) from entering the detection elements. Since shadow by the collimators also causes reduction in sensitivity of the X-ray detector, for example, a method of disposing the collimators on the separators to suppress the reduction in sensitivity to the minimum is adopted. Moreover, since the amount of X-rays incident on the detection elements varies depending on error of design of the collimators, for example, a method of segmentalizing detection elements to use only the part which receives X-rays (for example, see Patent Literature 1), a method of making the separators thicker than the collimators to absorb a margin of the error, and the like, are known.
Moreover, Patent Literature 2 discloses an X-ray measuring device in which an X-ray shielding member (collimator) is disposed so that a line passing on an X-ray focal spot and the center of a width of a blind part (separator) of a detection element passes on the center of a width of the X-ray shielding member, and in which a pitch in the array of X-ray shielding members is an integer multiple of two or larger of a pitch in the array of blind parts of detection elements.